The present invention relates to an illumination apparatus having a collimator lens, and more particularly to an illumination apparatus having a collimator lens that converts a convergent light beam to a collimated light beam.
In the past, a projection display apparatus was known such that a light emitted by an illumination apparatus illuminates a spatial light modulator and the light modulated by the spatial light modulator is projected onto a screen so as to display a picture image thereon.
Upon investigation by the inventor of the present invention, a configuration described below is presented.
As shown in FIG. 1, a light emitted from a light source 39 between a pair of opposing electrodes 37 of a light bulb 21 is reflected by a mirror 23, after which it is converted to a collimated light beam by a collimator lens 25, and enters into an integrator 31 having a first fly-eye lens 27 and a second fly-eye lens 29.
The fly-eye lenses 27 and 29 of the integrator 31, as observed from the direction of the optical axis O shown in FIG. 1, have tiny lens segments 27e and 29e, respectively, arranged in a matrix. The integrator 31 is configured so that each spot image of the light bulb 21 by the lens segments 27e of the first fly-eye lens 27 is correspondingly formed at the lens segments 29e of the second fly-eye lens 29. When viewed from the left side in the direction of the optical axis O in FIG. 1, each spot image 32 of the light bulb 21 formed at the lens segments 29e of the second fly-eye lens 29 appears as shown in FIG. 2.
Returning to FIG. 1, the light exiting from the second fly-eye lens 29 passes through a condenser lens 33, and then enters into a spatial light modulator 35.
The spatial light modulator 35 is an element that, by use of the birefringence of a liquid crystal, for example, imparts light modulation to its incident light in accordance with a video signal. In this case, the light from the light-collecting lens 33 is reflected by the spatial light modulator 35 as it is modulated thereby, so that the reflected light forms a video image on a screen (not shown in the drawing).
As shown in FIG. 1, the above-noted collimator lens 25 in general has simple spherical curved surfaces at its light entrance and exit surfaces.